Keying subjects crawling along ground

[Craig Parkes]

Hey guys - got a short film project coming up and am looking for some general advice with a potentially tricky key - likely to be shooting on RED.

The subjects need to be crawling, squirming along the ground, and we would ideally want to key out the ground below them so that we can composite them on top of each other so it looks like they are all crawling over each other (imagine a ball of warms) and growing outwards. It's for an artistically motivated short film - so achieving this artistic vision is the main goal but budget is quite limited.

Has anyone had experience shooting for and/or keying subjects in a similiar fashion? Obviously if we have them crawl directly along a green mat (i.e touching it) we have the issue of spill reflecting on them, and their shadows messing with the key. Also we would have next to no ability to light them dramatically as they would be getting hit with the same light that's lighting the screen.

So, has anyone used something like a platform with a see-through (perspex?) floor to create a similiar effect, or can give some perspective on what issues this would create ?

 

[Joel Kaye]

You should definitely shoot a test. That's going to be hard to key probably 'cause big spill on skin tones can really be tough. You might be better off shooting on black or white and doing a rough roto with a luma key.

You're probably going to have to roto this one if you really want it to look great. Otherwise a rough key might have to do.

The see through floor will have reflection issues but I think you could matte out the reflections easily. If you built something like this that was three levels you'd probably simplify post.

In the end I don't think people will look like they are crawling on each other unless they are really crawling on each other. But if this is more surreal than real that doesn't matter much.

 

[Craig Parkes]

Yeah, it's certainly more surreal than real - We've been thinking about the black, Luma and Roto as well - might be the way to go.

 

[FREUDENBERG_FILMS]

Don't forget to throw in a motion tracker so you have options for stabilizing and or tracking background elements.

 

[Dj Joofa]

There are keyers available that key (segment/isolate) objects out using motion instead of color information (green/blue screen). For e.g., I think Boris effects has such keyers. Please see if they work for you.